There are countless folks out there weighing their next career move. Everyone does it, and a lot of drivers find the scales tip in our favor – we’re a top of the line fleet and great driver support consistently attracts excellent new talent. But as an active recruiter and as a great American trucking company, Smith Transport also knows our “weigh” around scales of another common kind.
Experienced drivers know all about weigh scales, but not everyone knows just how they work. So, whether you’re a potential new driver or just a curious reader, let’s take a look at how scaling a tractor trailer works and learn the basics.
- Why do we weight in the first place?
Like many trucking regulations, Congress set regular big rig weight limits at a total weight of 80,000 pounds back in 1980. The reasons are fairly simple. First, if you’ve ever pushed a shopping cart, you surely noticed that starting, stopping, and otherwise controlling a heavy load is much harder than a lighter one. With the sheer number of vehicles and increasing speeds of travel these days, a heavy truck can become all the more hazardous. Less obvious, our hardened highways are not as tough as they may seem. More weight means more stress and more (expensive) damage—something we all want to avoid! This all goes back to why weight limits were put into play over 35 years ago, and why it’s still important today.
- There’s more than just one weight
The overall weight of a vehicle is what’s known as its “gross weight.” Think of stepping on to your bathroom scale after Thanksgiving – gross weight is the entire weight of the truck, trailer, cargo, fuel, etc. But weight is almost always provided to the truck driver split into three smaller figures, which can be affected by many factors and are often regulated separately:
Steer Axle – This is the weight over the front two (steering) wheels. Most states limit this to either 12,000 or 20,000 pounds. Less weight makes some sense as we are running less rubber up front and steering adds to the stress on our leading tread.
Drive Axle – This measurement covers the two axles immediately behind the cab which push the truck along. These are usually limited to 34,000 pounds.
Trailer Axle – Also regularly limited to 34,000 pounds, this figure represents the trailing two axles found at the very back end of a typical 18-wheeler. Their precise position and the ordering of cargo can have quite an effect here.
- There are many ways to weigh
No matter how you crunch the numbers, scales handle some serious abuse. Imagine weighing multi-ton vehicles all day, every day of the year, in every type of weather. So, how do they do it?
One-Axle – Taking it one step at a time, these scales take a new measurement as the driver moves each individual axle over the scale, adding it all up to reach a gross weight figure.
One-Stop – More like the scale at the doctor’s office, these platforms add the weight up all at once by reckoning gross weight over several strategically placed sensors under the entire truck.
Weigh-in-Motion – These are popular especially in more heavily trafficked stations. The advantage? Trucks can weigh in while rolling over the scale without stopping and keep America’s cargo on the move.
To be fair, we’ve only touched the surface of the issue here, but we hope we’ve shared a little new information with our new drivers and anyone else who may be interested. And for those experienced drivers that may know this stuff already, here’s something you may not have known:
Maybe it’s time to join Smith in the fast lane.